Liner bag for flexible bulk container

ABSTRACT

The design comprising bag ( 36 ) formed with deep side gussets ( 42, 44 ). It has a body portion and a neck. The front face, rear face and gussets are heat welded together at the base of the bag. At the neck ( 56 ) the front face is welded to the front sheets of the gussets and the rear face is welded to the rear sheets of the gussets so that the gusset can open at these parts. At the free ends of the neck ( 66 ) the front face, rear face and gussets are heat welded together to be held together when the bag is opened.

This invention relates to plastic bags and to methods of filling them.

The invention is concerned with such plastic bags which are used asliners (hereinafter called “liner bags”) for bulk bags for containingfree flowing moisture sensitive granular material. Hitherto such linerbags were used especially but not exclusively to line one tonne bulkbags for sugar. The bulk bags are normally woven plastics bags ofsufficient strength to carry such content and when filled with freeflowing granular material take up a cuboidal form. The upper surface ofthe bulk bag is open and a closure flap means is provided which spanthis open surface when the bulk bag has been filled to provide a closuretherefor. Loops are provided at the corners of the bulk bags so thatthey may be lifted by the forks of a fork lift truck. The liner bag isused to contain the granular material and to protect the contentsagainst ingress of contaminants and of air containing moisture andconsequent formation of lumps of sugar because of the water content ofthe air.

In known arrangements the liner bag is formed from blown plastic tubenormally formed with deep gussets so as to be able to take up thecuboidal shape. In the lie flat condition, the liner bag comprises afront panel and a rear panel and each gusset comprises a front gussetpart and a rear gusset part, the side edges of the front panel beingjoined to the front gusset parts and the side edges rear panel beingjoined to the rear gusset parts. The liner is longer than the bulk bagand is of constant width. Its upper end is not sealed. The liner bag isinserted into the bulk bag and its upper end is opened to receive thefiller nozzle through which sugar is delivered into the liner bag. Inmany cases initially a blast of air causes the liner bag to expandwhereafter the granular material is fed into the liner bag through thenozzle. After filling the liner bag, in most cases, is vibrated causingthe sugar settle to a maximum level. The upper portion of the liner bagis wound around and twisted after which it is wire tied and knotted ortaped to seal it. To transport the material, the bulk bag is lifted bythe loops and the upper portion of the liner bag may also form aretaining part that is also secured to the lifting device. The base ofthe bulk bag has an opening therein normally closed by a bottom flap. Todischarge the contents of the bulk bag, it is located above the materialreceptacle. The top opening is opened, the wire ties and tape areremoved and the knot undone. The bottom flap is opened and the liner bagis pierced so that the sugar will flow out of the liner bag.

Such a system is widely used in the sugar industry. It does howeversuffer from a number of disadvantages. First, the knot (together withthe wire ties and the adhesive tape) often does not provide an adequateseal so that the sugar may be contacted by the water content in theambient air so that it becomes lumpy. Second, it is relatively easy toundo and re-tie the wire ties and the knot so that the bulk bags areliable to pilferage which cannot be easily visually detected.

U.S. Pat. No. 4,341,054 (Courtheoux) discloses heat welding the mouth ofa plastic bag. The bag is small, being designed to accommodate 2500 gmof liquid syrup and is not gusseted. Thus there are no undue technicaldifficulties in heat welding the bag. However it is not possible toadapt this teaching to liner bags for bulk bags because the length ofthe required heat weld would be of the order of two metres and the linerbags would be deeply gusseted. In practice it has hitherto beenextremely difficult to place the various panels of the liner bag flatand close together and consequently there will be folds in the plasticsheeting which will prevent the formation of a satisfactory moistureproof sealing of the plastic parts. In particular it would not bepossible to do so speedily as would be required for normal commercialoperation.

U.S. Pat. Nos. 4,596,040 and 4,781,475 (La Fleur et al) disclose a linerfor a bulk bag. The bulk bag is of a particular shape with a nozzle orthroat at its upper end and the liner bag is shaped to correspond to theshape of the bulk bag. The liner bag is heavily gusseted to take up thecuboidal shape and has a reduced dimensioned neck into which the gussetextends. The nozzle is closed by being tied off by a cord. This suffersfrom the disadvantages of inadequate sealing and liability to pilferageas mentioned above.

According to one aspect of the invention there is provided a liner bagcomprising a front panel, a rear panel and gussets between the sides ofthe panels, each gusset comprising a front gusset part and a rear gussetpart, the side edges of the front panel being joined to the front gussetparts and the side edges of the rear panel being joined to the reargusset parts, the liner bag comprising a body part and a neck at itsupper end, which neck is adapted to receive therein a filling nozzle andwhich neck can be heat sealed after the liner bag has been filled toseal liner bag, the neck being formed by welding together the edges ofthe front panel to the front gusset parts and by welded together theedges of the rear panel to the rear of gusset parts; wherein the frontand rear panels and the gusset parts are all welded together only at thefree end of the neck.

According to another aspect of the invention there is provided a methodof manufacturing a liner bag as set out in the preceding paragraphcomprising forming a gusseted lay flat tube; passing the tube over awelding table; by means of a welding unit, welding the tube to form theneck; and interposing blanking pieces between the front and rear partsof the gussets to prevent the front panel and front gusset parts frombeing welded to the rear panel and rear gusset part and locating suchblanking pieces so that they, the blanking pieces, are spaced from theend of the neck with the result that the front panel, the front gussetparts, the rear gusset parts and the rear panel are welded together atsuch spaced locations.

According to a further aspect of the invention there is provided amethod of filling a bulk bag with free flowing material e.g. sugar, inwhich a liner bag, as set out in the preceding paragraph but one, isinserted into the bulk bag, the neck is opened and placed around thefiller nozzle of a bulk filling machine, and the liner bag is filled,wherein inward pressure is then applied between the gusset parts tore-form the gussets and cause the panels and gusset parts to lie flatagainst one another and then heat sealing the panels and the gussetparts at the part of the neck near the body part to seal the liner bagclosed.

According to a further aspect or the invention there is provided thecombination of a bulk bag containing therein a liner bag of theinvention as set forth above, the bulk bag having an open top and flapmeans which closes the open top when the bag is filled.

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings.

In the drawings:

FIG. 1 shows diagrammatically the filling of a sugar bulk bag,

FIG. 2 is a plan view of a liner bag in the lay flat condition,

FIG. 3 is a side view of the liner bag in the lay flat condition,

FIG. 4 is a perspective view of the liner bag in the partially filledcondition,

FIG. 5 is a perspective view of a bulk bag,

FIG. 6 is an underplan view of the bulk bag showing the outlet neck inthe closed position,

FIG. 7 is a perspective view of the underside of the bulk bag with thedischarge nozzle extended,

FIG. 8 is a diagrammatic plan of the manufacturing table on which theliner bag is made,

FIG. 9 is a view similar to FIG. 2 of a modified liner bag of theinvention,

FIG. 10 is a back view of a sealing unit, and

FIG. 11 is a section on line 11—11 of FIG. 10 showing the sealing unitin use applying a heat seal to the neck of the liner bag.

Referring now to FIG. 1, there is shown a filler station 10 for fillinga bulk bag 12 with sugar. The filler station 10 includes a 400 mm o/dnozzle 14 leading from a sugar hopper or silo (not shown) and a conveyor16 on which the bulk bag 12 is delivered to below the nozzle 14.

The bulk bag 12 comprises a bag formed of woven polypropylene andincorporating four loops 18 by means of which the bulk bag may be liftedby a fork lift carrier. The upper end of the bulk bag 12 is open. Thewalls of the bulk bag have a top extension 20 (see FIG. 5). A cord 24 isprovided for tying extension parts together to close the opening. At thebottom end 26, the bag 12 has a cylindrical release nozzle or neck 28(see FIGS. 6 and 7). Eyelets 30 are provided near the end of the releasenozzle 28. A draw cord 32 passes through the eyelets 30 to draw the necknozzle 28 closed to form a continuation of the bottom end 26 of the bag.An extension skirt 34 of more flexible material extends from the end ofthe neck or nozzle 28. When the neck is being collapsed, the material ofthe skirt 34 serves to assist closing off the opening surrounded by thenozzle or neck 28. The bulk bag 12 is of an appropriate size to containone thousand kilograms (one tonne) of sugar. It is of approximatelycuboidal shape (and will be referred to as a cube herein).

As thus far described the parts are conventional and known to thoseskilled in the art.

Within the bulk bag 12 is a liner bag 36. The liner bag 36 is a heavilygusseted plastic bag formed from blown plastic tubing and comprising, inthe lay flat condition, a front panel 38 and a rear panel 40. Eachgusset 42 and 44 comprises a front gusset panel or part 46 and a reargusset panel or part 48 (best shown in FIG. 4). The side edges 38 a ofthe front panel 38 merge with the side edges of the front gusset parts46 and the side edges 40 a of the rear panel 40 merge with the sideedges of the rear gusset parts 48. The material of the liner is lowdensity polyethylene or linear low density polyethylene of 100 μm (onehundred micron) thickness. The bottom edge 50 of the liner bag 36 issealed off by a double seal 52 which seals together the bottom edges ofthe front and rear panels and the gusset parts.

The upper edge 54 of the liner bag 36 is partially closed and leads toan elongated neck 56 that extends over a small portion of this upperedge 54, thus forming the liner bag into a body 58 and a neck 56 withthe edge 54 at the join therebetween. The upper edge 54 has a curvedconcave portion 62 leading to the neck 56. The outer parts 64 of theupper edge 54 are curved convexly downwards towards the bottom of theliner bag 36. The gussets 42 and 44 extend into the neck 56. At theupper edges 54 and the side edges 60 of the neck 56, the front panel 38is heat welded to the outer edges of the front gusset parts 46 and therear panel 40 is heat welded to the outer edges of the rear gusset parts48. The front and rear panels and the front and rear gusset parts arenot welded together at these edges except as will be described. The sizeof the neck 56 is such that when expanded it is of sufficient size tofit relatively closely over the filling nozzle 14 to which it may besecured as will be described. At the upper or free end of the neck 56there are short welds 66 connecting together the front panel 38, thefront and rear gusset parts 46 and 48 and the rear panel 40.

The effect of the deep gussets 42 and 44 is that when the liner bag 36is filled, the body 58 takes a substantially cube shape. All welds aredouble welds for requisite strength purposes.

A suitable clamping device (not shown) clamps the neck 56 to the fillingnozzle 14. An air release valve (also not shown) is provided in thefilling nozzle to permit the escape of air in the liner bag 36 which isdisplaced by the sugar.

A sealing unit 100 (see FIGS. 10 and 11) is provided for sealing theneck 56. The unit 100 comprises a pair of jaws carried from a top bar104 fixed above a position on the conveyor beside the filler station.The top bar 104 carries a cross member 106 at its ends by means of apair of widely spaced pneumatic cylinders 108 which permit the crossmember 106 to move upwards and downwards under the control of a workman.The cross member 106 has two spaced bars 110 connected together at itsends. The cross member 106 carries a fixed jaw 114 and carrier bar 116.The carrier bar 116 carries a movable sealing jaw 118 by means of threepneumatic cylinders 120. A control box 122, having the appropriatecontrol buttons 124, is carried at one end of the top bar 104.

In use, the bulk bag 12, with the liner bag 36 therein, is brought tothe filler station 10 adjacent to the filling nozzle 14. The neck 56 isfitted over the filling nozzle 14 with the welds 66 manipulated to be inpositions at opposite ends of a diameter of the filling nozzle 14 whichis parallel to the front and rear panels 38 and 40 (and the walls of thebulk bag 12 against which they will lie when the liner 36 is filled).The neck 56 is secured to the filling nozzle e.g by a binding cord orthe like. A short blast of air expands the liner bag 36. Sugar is nowdelivered through the nozzle 14 via the neck 56 into the body 58 of theliner bag 36. When the appropriate amount of sugar has been delivered,the liner bag 36 will be filled up to the upper edge 54 of the liner bag36. Because of the provision of the gussets 42 and 44, the liner bag 36will take up a generally cuboidal shape (as is shown in FIG. 1). Thebulk bag 12 is vibrated so that the sugar will spread and the uppersurface of the sugar will be flattened from the coned position that ittakes up due to delivery from the filling nozzle 14. Workmen on oppositesides of the filling nozzle now push lightly into the join of the gussetparts 46 and 48 which causes the gussets 42 and 44 to collapse and allthe panels to lie flat against each other re-forming to its original layflat condition. The neck will be folded over to lie flat on the body ofthe liner bag.

The bulk bag 12 is moved to the next station at which the sealing unit100 is located. The neck panels 56, which now lie flat against eachother, are threaded through the gap between the fixed and movablesealing jaws 114 and 118 and the gap between the bars forming the crossmember, the cross member 106 having been drawn downwardly to close tothe upper surface of the filled liner bag 20. On application of theappropriate control button 124, the movable sealing jaw 118 is movedtowards the fixed jaw 114 and the neck sealed closed. The movable jaw118 is caused to move away and the upper part of the neck 56 is removedfrom the gap between the jaws there being a short length of neck belowthe seal. The cylinders 108 lift the cross member 106 to its restposition.

The bulk bag 12 is now moved to the next station where the cord 24wrapped around the extension flaps 20 to tie them closed.

The time of the filling cycle i.e. from bringing the bulk bag 12 to thefilling station 10 and moving it to the next station and replacing it bythe next bag will be of the order of forty (40) seconds.

The sugar can be stored and transported in the liner bags 36 within thebulk bag 12. When it is desired to discharge the sugar, the bulk bag 12is lifted over the hopper or other receptacle into which the sugar is tobe delivered. The cord 32 is released permitting the discharging nozzleor neck 28 to take up its discharge position (as shown in FIG. 7). Theextension flaps 20 are opened and the upper end of the liner bag is cut.A knife or spear cuts through the exposed part of the liner bag 36 atthe discharge neck 28 and the sugar escapes through the opening thusformed and is delivered to the receptacle. We have found by piercing theupper end of the liner bag, air will flow into the liner bag as thesugar is discharged and that the liner bag 36 is not drawn down with thesugar during discharge but remains within the bulk bag 12.

The dimensions of the liner bag 36 are (in the lay flat condition) asfollows: width 1200 mm, depth of gussets 400 mm, height (i.e. betweenthe edge 50 and the lowest part of the edge 54) 1950 mm, width of neck760 mm, length of neck 800 mm and distance from the join of the frontedge 54 to the side edges of the panels to the beginning of the neck is250 mm. The length of the short welds is 150 mm. A liner bag of thesedimensions will accept one tonne of sugar.

The plastic material of which the liner bag 36 is made, contains asufficient amount of anti-blocking agent so that the neck 56 can beeasily and quickly opened for fitting on to the nozzle 14.

The lay flat material 68 from which the liner bags 36 are made isprovided on a roll 70 (see FIG. 8) rotatably mounted at one end of ametal welding table 72 over which the material 68 is drawn. A shapedwelding unit is supported in a manner known per se and is moveddownwardly to weld the various parts of the material together Theposition of a unit is indicated by the weld lines that it forms and theconstruction thereof will be understood by those skilled in the art. Theunit has a cross piece 74 that forms the transverse double seal 52.Further, the unit comprises two side pieces 78 that each form a part ofthe upper edge 54 and a side 60 of the neck 56. Secured to the table 72are two blanking sheets 80 of “Teflon”® which are located respectivelywithin the gussets 42 and 44. These sheets 80 blank off the weld linesof the side pieces 78 except for a short space 79 adjacent to the crosspiece 74. Thus when the unit acts on the lay flat tube, the side pieces78 will weld together the front and rear panels 38 and 40 respectivelyto the front and rear gusset parts 46 and 48 and, only at the said space79 will weld the front and rear panels and the front and rear gussetparts all together. Workmen on either side of the table 72 now pull awaythe material between the welds formed by the unit and the edges 36 a ofthe liner bag 36. This material will comprise about ten per cent (10%)of the material of the liner bag and is sent away for re-processing. Thematerial is moved forwardly and is cut between the bottom seal 52 andthe top of the neck 56.

Reference should be made to FIG. 9 in which is shown a liner bag 84 thatis adapted to contain cement. The liner bag 84 is similar to the linerbag 36 save that a discharge neck 86 is provided at the lower end. Theshape of the lower edge 88 and discharge neck 86 replicates the shape ofthe upper edge 54 and neck 56. The welds 90 forming such edge 88 andneck 86 however extend to join together all four panels i.e. the frontpanel, the front gusset part, the rear gusset part and the rear panel.Further the end of the neck 86 is closed by a cross-weld 92.

The liner bag 84 may be made of sufficiently strong material so as toserve as a container bag without the necessity of using the bulk bag.

We have found that because the neck 26 is relatively narrow, the panelswill lie flat against each other with a minimum of, or indeed totalelimination of, folds and creases. Thus the sealing of the material ofthe neck can be effected quickly and efficiently. The seal will be suchthat there can be no ingress of contaminants, air or water into thegranular material within the liner bag 20. Furthermore it is notpossible to remove any of the granular material without damaging theliner bag which will minimize pilferage.

We have found that the bags above mentioned can be filled each with onetonne of product at the rate of forty five per half hour, i.e. at aboutone every forty seconds. Because of the fact that the upper portions ofthe side edge of the neck are welded together at 66, the neck 56collapses easily and quickly when treated as mentioned above. This is ofconsiderable importance as otherwise the panels and gusset parts mayincorporate folds so that proper sealing of the material is notpossible. In this connection it should be borne in mind that it isextremely difficult otherwise to collapse the neck and all the more soif one endeavours to do so within the time constraints mentioned above.

We have found surprisingly with the sugar filled liner bag 36, liquidcollects in the folded over neck of the liner bag. Thus not only is thecontent of the liner bag protected from the ingress of water laden air,but also is dried because the liquid in the sealed liner bag finds itsway into the neck.

It will be noted that there is a minimum of action taken by hand at theneck of the liner bag during sealing and discharge. Thus the possibilityof extraneous matter dropping into the liner bag, as happened hitherto,is virtually eliminated.

The invention is not limited to the precise constructional detailshereinbefore described and illustrated in the drawings. For example theliner bag can be used as a liner bag for bulk bags for any other freeflowing product such as salt, achaar and other products includingchemicals. The dimensions of the various parts can be varied as desiredand the liner bags can be designed for bulk bags of differentcapacities. The wall thickness of the lay flat tube may be different.Thicknesses as low as 40 μm have been used. It is important of coursethat the walls of the liner bag are of adequate strength. The liner bagcan be made of any other suitable plastic material such as polypropyleneor of co-extruded plastics.

The liner bag can be used with different bulk bags including bulk bagshaving only two closure flaps, neck arrangements and simple cord devicesto wrap around the neck or closure flaps to close off the top of thebulk bag. The bulk bag can have an upper opening similar to thedischarge neck. The liner bag can be used with crates or othercontainers to contain and store any other moisture sensitive freeflowing granular material.

The liner bag can also be used as a bulk bag for smaller or otheramounts of material provided that the material whereof the liner bag ismade is of sufficient strength and thickness.

What is claimed is:
 1. A liner bag comprising: a front panel having sideedges, a rear panel having side edges, and gussets between the sideedges of the front and rear panels, each gusset comprising a frontgusset part and a rear gusset part, the side edges of the front panelbeing joined to the front gusset parts and the side edges of the rearpanel being joined to the rear gusset parts, the liner bag having a bodypart and a neck at its upper end, which neck is adapted to receivetherein a filling nozzle and which neck can be heat sealed after theliner bag has been filled to seal the liner bag, the neck being formedby sealing together the edges of the front panel to the front gussetparts and by sealing together the edges of the rear panel to the rear ofgusset parts; wherein the front and rear panels and the gusset parts areall sealed together only at the free end of the neck.
 2. A liner bag asclaimed in claim 1, wherein the gusset parts are welded together byshort welds, the length of the short welds being less then 20% of thelength of the neck.
 3. A liner bag as claimed in a claim 1, furthercomprising an upper edge at the join of the body and the neck whereinthe upper edge is curved and convex at its outer ends.
 4. A method ofmanufacturing a liner bag as claimed in claim 1 comprising the steps of:forming a gusseted lay flat tube; passing the tube over a welding table;welding the tube to form the neck by means of a welding unit; andinterposing blanking pieces between the front and rear parts of thegussets to prevent the front panel and front gusset parts from beingwelded to the rear panel and rear gusset parts; wherein the blankingpieces are located so that they, the blanking pieces, are spaced fromthe end of the neck with the result that the front panel, the frontgusset part, the rear gusset part and the rear panel are welded togetherat spaced locations.
 5. A method of manufacturing a liner bag as claimedin claim 4 wherein the welding unit seals the end of the adjacent linerbag at the same time as it forms the neck.
 6. A method of filling a bulkbag with free flowing material in which a liner bag as claimed in claim1 is inserted into the bulk bag, the neck is opened and placed aroundthe filler nozzle of a bulk filling machine, and the liner bag is filledwherein inward pressure is applied to the sides of the neck between thegusset parts to re-form the gussets and to cause the panels and gussetparts to lie flat against one another, and the panels and the gussetparts are heat sealed at the lower part of the neck to seal the linerbag closed.
 7. The combination of a bulk bag containing therein a linerbag as claimed in claim 1, wherein the bulk bag has an open top and aflap which closes the open top when the bag is filled.
 8. A liner bag asclaimed in claim 2, further comprising an upper edge at the join of thebody and the neck, wherein the upper edge is curved and convex at itsouter ends.
 9. A liner bag comprising: a front panel having side edges;a rear panel having side edges; and gussets between the side edges ofthe front and rear panels, each gusset comprising a front gusset partand a rear gusset part, the side edges of the front panel being joinedto the front gusset parts and the side edges of the rear panel beingjoined to the rear gusset parts, the liner bag having a body part and aneck at its upper end, which neck is adapted to receive therein afilling nozzle and which neck can be heat sealed after the liner bag hasbeen filled to seal the liner bag, the neck being formed by weldingtogether the edges of the front panel to the front gusset parts and bywelding together the edges of the rear panel to the rear of gussetparts; wherein the front and rear panels and the gusset parts are allwelded together by short welds, the length of the short welds being lessthen 20% of the length of the neck.
 10. A method of manufacturing aliner bag having a front panel having side edges, a rear panel havingside edges, and gussets between the side edges of the front and rearpanels, each gusset including a front gusset part and a rear gussetpart, the side edges of the front panel being joined to the front gussetparts and the side edges of the rear panel being joined to the reargusset parts, where the liner bag has a body part and a neck at itsupper end, which neck is adapted to receive therein a filling nozzle andwhich neck can be heat sealed after the liner bag has been filled toseal the liner bag, and the neck is formed by welding together the edgesof the front panel to the front gusset parts and by welding together theedges of the rear panel to the rear of gusset parts so that the frontand rear panels and the gusset parts are all welded together by shortwelds only at the free end of the neck; and the method comprising thesteps of: forming a gusseted lay flat tube; passing the tube over awelding table; welding the tube to form the neck by means of a weldingunit; and interposing blanking pieces between the front and rear partsof the gussets to prevent the front panel and front gusset parts frombeing welded to the rear panel and rear gusset parts; wherein theblanking pieces are located so that they, the blanking pieces, arespaced from the end of the neck with the result that the front panel,the front gusset part, the rear gusset part and the rear panel arewelded together at spaced locations.